Synthesis of optically-active benzylic amines; asymmetric reduction of ketoxime ethers with chiral oxazaborolidines

The preparation of novel optically active benzylic amines by the enantio selective reduction of phenone oximes using chiral oxazaborolidine is described. The choice of the chiral 1,2-amino alcohol (S)-diphenylvalinol as chiral inducer and that of the benzyl group for the O-oxime substituent is explained. 23 primary amines are obtained, with high enantio selectivity (e.e. = 98%), good yield (74%) on preparative scale. A mechanistic explanation is proposed. (C) 2001 Elsevier Science Ltd. All rights reserved.